smatch_math.c

   1 /*
   2  * Copyright (C) 2010 Dan Carpenter.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17
  18 #include "symbol.h"
  19 #include "smatch.h"
  20 #include "smatch_slist.h"
  21 #include "smatch_extra.h"
  22
  23 static struct range_list *_get_rl(struct expression *expr, int implied, int *recurse_cnt);
  24 static struct range_list *handle_variable(struct expression *expr, int implied, int *recurse_cnt);
  25 static struct range_list *(*custom_handle_variable)(struct expression *expr);
  26
  27 static sval_t zero  = {.type = &int_ctype, {.value = 0} };
  28 static sval_t one   = {.type = &int_ctype, {.value = 1} };
  29
  30 struct range_list *rl_zero(void)
  31 {
  32         return alloc_rl(zero, zero);
  33 }
  34
  35 struct range_list *rl_one(void)
  36 {
  37         return alloc_rl(one, one);
  38 }
  39
  40 enum {
  41         RL_EXACT,
  42         RL_HARD,
  43         RL_FUZZY,
  44         RL_IMPLIED,
  45         RL_ABSOLUTE
  46 };
  47
  48 static struct range_list *last_stmt_rl(struct statement *stmt, int implied, int *recurse_cnt)
  49 {
  50         if (!stmt)
  51                 return NULL;
  52
  53         stmt = last_ptr_list((struct ptr_list *)stmt->stmts);
  54         if (stmt->type != STMT_EXPRESSION)
  55                 return NULL;
  56         return _get_rl(stmt->expression, implied, recurse_cnt);
  57 }
  58
  59 static struct range_list *handle_expression_statement_rl(struct expression *expr, int implied, int *recurse_cnt)
  60 {
  61         return last_stmt_rl(get_expression_statement(expr), implied, recurse_cnt);
  62 }
  63
  64 static struct range_list *handle_ampersand_rl(struct expression *expr, int implied, int *recurse_cnt)
  65 {
  66         struct range_list *rl;
  67
  68         if (implied == RL_EXACT || implied == RL_HARD)
  69                 return NULL;
  70         if (get_address_rl(expr, &rl))
  71                 return rl;
  72         return alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
  73 }
  74
  75 static struct range_list *handle_negate_rl(struct expression *expr, int implied, int *recurse_cnt)
  76 {
  77         if (known_condition_true(expr->unop))
  78                 return rl_zero();
  79         if (known_condition_false(expr->unop))
  80                 return rl_one();
  81
  82         if (implied == RL_EXACT)
  83                 return NULL;
  84
  85         if (implied_condition_true(expr->unop))
  86                 return rl_zero();
  87         if (implied_condition_false(expr->unop))
  88                 return rl_one();
  89         return alloc_rl(zero, one);
  90 }
  91
  92 static struct range_list *handle_bitwise_negate(struct expression *expr, int implied, int *recurse_cnt)
  93 {
  94         struct range_list *rl;
  95         sval_t sval;
  96
  97         rl = _get_rl(expr->unop, implied, recurse_cnt);
  98         if (!rl_to_sval(rl, &sval))
  99                 return NULL;
 100         sval = sval_preop(sval, '~');
 101         sval_cast(get_type(expr->unop), sval);
 102         return alloc_rl(sval, sval);
 103 }
 104
 105 static struct range_list *handle_minus_preop(struct expression *expr, int implied, int *recurse_cnt)
 106 {
 107         struct range_list *rl;
 108         sval_t sval;
 109
 110         rl = _get_rl(expr->unop, implied, recurse_cnt);
 111         if (!rl_to_sval(rl, &sval))
 112                 return NULL;
 113         sval = sval_preop(sval, '-');
 114         return alloc_rl(sval, sval);
 115 }
 116
 117 static struct range_list *handle_preop_rl(struct expression *expr, int implied, int *recurse_cnt)
 118 {
 119         switch (expr->op) {
 120         case '&':
 121                 return handle_ampersand_rl(expr, implied, recurse_cnt);
 122         case '!':
 123                 return handle_negate_rl(expr, implied, recurse_cnt);
 124         case '~':
 125                 return handle_bitwise_negate(expr, implied, recurse_cnt);
 126         case '-':
 127                 return handle_minus_preop(expr, implied, recurse_cnt);
 128         case '*':
 129                 return handle_variable(expr, implied, recurse_cnt);
 130         case '(':
 131                 return handle_expression_statement_rl(expr, implied, recurse_cnt);
 132         default:
 133                 return NULL;
 134         }
 135 }
 136
 137 static struct range_list *handle_divide_rl(struct expression *expr, int implied, int *recurse_cnt)
 138 {
 139         struct range_list *left_rl, *right_rl;
 140         struct symbol *type;
 141
 142         type = get_type(expr);
 143
 144         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 145         left_rl = cast_rl(type, left_rl);
 146         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 147         right_rl = cast_rl(type, right_rl);
 148
 149         if (!left_rl || !right_rl)
 150                 return NULL;
 151         if (is_whole_rl(left_rl) || is_whole_rl(right_rl))
 152                 return NULL;
 153
 154         return rl_binop(left_rl, '/', right_rl);
 155 }
 156
 157 static struct range_list *handle_subtract_rl(struct expression *expr, int implied, int *recurse_cnt)
 158 {
 159         struct symbol *type;
 160         struct range_list *left_rl, *right_rl;
 161         sval_t max, min, tmp;
 162         int comparison;
 163
 164         type = get_type(expr);
 165         comparison = get_comparison(expr->left, expr->right);
 166
 167         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 168         left_rl = cast_rl(type, left_rl);
 169         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 170         right_rl = cast_rl(type, right_rl);
 171
 172         if ((!left_rl || !right_rl) &&
 173             (implied == RL_EXACT || implied == RL_HARD || implied == RL_FUZZY))
 174                 return NULL;
 175
 176         if (!left_rl)
 177                 left_rl = alloc_whole_rl(type);
 178         if (!right_rl)
 179                 right_rl = alloc_whole_rl(type);
 180
 181         /* negative values complicate everything fix this later */
 182         if (sval_is_negative(rl_min(right_rl)))
 183                 return NULL;
 184         max = rl_max(left_rl);
 185
 186         switch (comparison) {
 187         case '>':
 188         case SPECIAL_UNSIGNED_GT:
 189                 min = sval_type_val(type, 1);
 190                 max = rl_max(left_rl);
 191                 break;
 192         case SPECIAL_GTE:
 193         case SPECIAL_UNSIGNED_GTE:
 194                 min = sval_type_val(type, 0);
 195                 max = rl_max(left_rl);
 196                 break;
 197         default:
 198                 if (sval_binop_overflows(rl_min(left_rl), '-', rl_max(right_rl)))
 199                         return NULL;
 200                 min = sval_type_min(type);
 201         }
 202
 203         if (!sval_binop_overflows(rl_min(left_rl), '-', rl_max(right_rl))) {
 204                 tmp = sval_binop(rl_min(left_rl), '-', rl_max(right_rl));
 205                 if (sval_cmp(tmp, min) > 0)
 206                         min = tmp;
 207         }
 208
 209         if (!sval_is_max(rl_max(left_rl))) {
 210                 tmp = sval_binop(rl_max(left_rl), '-', rl_min(right_rl));
 211                 if (sval_cmp(tmp, max) < 0)
 212                         max = tmp;
 213         }
 214
 215         if (sval_is_min(min) && sval_is_max(max))
 216                 return NULL;
 217
 218         return cast_rl(type, alloc_rl(min, max));
 219 }
 220
 221 static struct range_list *handle_mod_rl(struct expression *expr, int implied, int *recurse_cnt)
 222 {
 223         struct range_list *rl;
 224         sval_t left, right, sval;
 225
 226         if (implied == RL_EXACT) {
 227                 if (!get_value(expr->right, &right))
 228                         return NULL;
 229                 if (!get_value(expr->left, &left))
 230                         return NULL;
 231                 sval = sval_binop(left, '%', right);
 232                 return alloc_rl(sval, sval);
 233         }
 234         /* if we can't figure out the right side it's probably hopeless */
 235         if (!get_implied_value(expr->right, &right))
 236                 return NULL;
 237
 238         right = sval_cast(get_type(expr), right);
 239         right.value--;
 240
 241         rl = _get_rl(expr->left, implied, recurse_cnt);
 242         if (rl && rl_max(rl).uvalue < right.uvalue)
 243                 right.uvalue = rl_max(rl).uvalue;
 244
 245         return alloc_rl(zero, right);
 246 }
 247
 248 static sval_t sval_lowest_set_bit(sval_t sval)
 249 {
 250         int i;
 251         int found = 0;
 252
 253         for (i = 0; i < 64; i++) {
 254                 if (sval.uvalue & 1ULL << i) {
 255                         if (!found++)
 256                                 continue;
 257                         sval.uvalue &= ~(1ULL << i);
 258                 }
 259         }
 260         return sval;
 261 }
 262
 263 static struct range_list *handle_bitwise_AND(struct expression *expr, int implied, int *recurse_cnt)
 264 {
 265         struct symbol *type;
 266         struct range_list *left_rl, *right_rl;
 267         sval_t known;
 268
 269         if (implied != RL_IMPLIED && implied != RL_ABSOLUTE)
 270                 return NULL;
 271
 272         type = get_type(expr);
 273
 274         if (get_implied_value(expr->left, &known)) {
 275                 sval_t min;
 276
 277                 min = sval_lowest_set_bit(known);
 278                 left_rl = alloc_rl(min, known);
 279                 left_rl = cast_rl(type, left_rl);
 280                 add_range(&left_rl, sval_type_val(type, 0), sval_type_val(type, 0));
 281         } else {
 282                 left_rl = _get_rl(expr->left, implied, recurse_cnt);
 283                 if (left_rl) {
 284                         left_rl = cast_rl(type, left_rl);
 285                         left_rl = alloc_rl(sval_type_val(type, 0), rl_max(left_rl));
 286                 } else {
 287                         if (implied == RL_HARD)
 288                                 return NULL;
 289                         left_rl = alloc_whole_rl(type);
 290                 }
 291         }
 292
 293         if (get_implied_value(expr->right, &known)) {
 294                 sval_t min, left_max, mod;
 295
 296                 min = sval_lowest_set_bit(known);
 297                 right_rl = alloc_rl(min, known);
 298                 right_rl = cast_rl(type, right_rl);
 299                 add_range(&right_rl, sval_type_val(type, 0), sval_type_val(type, 0));
 300
 301                 if (min.value != 0) {
 302                         left_max = rl_max(left_rl);
 303                         mod = sval_binop(left_max, '%', min);
 304                         if (mod.value) {
 305                                 left_max = sval_binop(left_max, '-', mod);
 306                                 left_max.value++;
 307                                 if (left_max.value > 0 && sval_cmp(left_max, rl_max(left_rl)) < 0)
 308                                         left_rl = remove_range(left_rl, left_max, rl_max(left_rl));
 309                         }
 310                 }
 311         } else {
 312                 right_rl = _get_rl(expr->right, implied, recurse_cnt);
 313                 if (right_rl) {
 314                         right_rl = cast_rl(type, right_rl);
 315                         right_rl = alloc_rl(sval_type_val(type, 0), rl_max(right_rl));
 316                 } else {
 317                         if (implied == RL_HARD)
 318                                 return NULL;
 319                         right_rl = alloc_whole_rl(type);
 320                 }
 321         }
 322
 323         return rl_intersection(left_rl, right_rl);
 324 }
 325
 326 static struct range_list *handle_bitwise_OR(struct expression *expr, int implied, int *recurse_cnt)
 327 {
 328         struct symbol *type;
 329         struct range_list *left_rl, *right_rl;
 330
 331         if (implied != RL_IMPLIED && implied != RL_ABSOLUTE)
 332                 return NULL;
 333
 334         type = get_type(expr);
 335
 336         get_absolute_rl(expr->left, &left_rl);
 337         get_absolute_rl(expr->right, &right_rl);
 338         left_rl = cast_rl(type, left_rl);
 339         right_rl = cast_rl(type, right_rl);
 340         if (!left_rl || !right_rl)
 341                 return NULL;
 342
 343         return rl_binop(left_rl, '|', right_rl);
 344 }
 345
 346 static struct range_list *handle_right_shift(struct expression *expr, int implied, int *recurse_cnt)
 347 {
 348         struct range_list *left_rl;
 349         sval_t right;
 350         sval_t min, max;
 351
 352         if (implied == RL_EXACT || implied == RL_HARD)
 353                 return NULL;
 354
 355         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 356         if (left_rl) {
 357                 max = rl_max(left_rl);
 358                 min = rl_min(left_rl);
 359         } else {
 360                 if (implied == RL_FUZZY)
 361                         return NULL;
 362                 max = sval_type_max(get_type(expr->left));
 363                 min = sval_type_val(get_type(expr->left), 0);
 364         }
 365
 366         if (get_implied_value(expr->right, &right)) {
 367                 min = sval_binop(min, SPECIAL_RIGHTSHIFT, right);
 368                 max = sval_binop(max, SPECIAL_RIGHTSHIFT, right);
 369         } else if (!sval_is_negative(min)) {
 370                 min.value = 0;
 371                 max = sval_type_max(max.type);
 372         } else {
 373                 return NULL;
 374         }
 375
 376         return alloc_rl(min, max);
 377 }
 378
 379 static struct range_list *handle_left_shift(struct expression *expr, int implied, int *recurse_cnt)
 380 {
 381         struct range_list *left_rl, *res;
 382         sval_t right;
 383         sval_t min, max;
 384         int add_zero = 0;
 385
 386         if (implied == RL_EXACT || implied == RL_HARD)
 387                 return NULL;
 388         /* this is hopeless without the right side */
 389         if (!get_implied_value(expr->right, &right))
 390                 return NULL;
 391         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 392         if (left_rl) {
 393                 max = rl_max(left_rl);
 394                 min = rl_min(left_rl);
 395                 if (min.value == 0) {
 396                         min.value = 1;
 397                         add_zero = 1;
 398                 }
 399         } else {
 400                 if (implied == RL_FUZZY)
 401                         return NULL;
 402                 max = sval_type_max(get_type(expr->left));
 403                 min = sval_type_val(get_type(expr->left), 1);
 404                 add_zero = 1;
 405         }
 406
 407         max = sval_binop(max, SPECIAL_LEFTSHIFT, right);
 408         min = sval_binop(min, SPECIAL_LEFTSHIFT, right);
 409         res = alloc_rl(min, max);
 410         if (add_zero)
 411                 res = rl_union(res, rl_zero());
 412         return res;
 413 }
 414
 415 static struct range_list *handle_known_binop(struct expression *expr)
 416 {
 417         sval_t left, right;
 418
 419         if (!get_value(expr->left, &left))
 420                 return NULL;
 421         if (!get_value(expr->right, &right))
 422                 return NULL;
 423         left = sval_binop(left, expr->op, right);
 424         return alloc_rl(left, left);
 425 }
 426
 427 static int has_actual_ranges(struct range_list *rl)
 428 {
 429         struct data_range *tmp;
 430
 431         FOR_EACH_PTR(rl, tmp) {
 432                 if (sval_cmp(tmp->min, tmp->max) != 0)
 433                         return 1;
 434         } END_FOR_EACH_PTR(tmp);
 435         return 0;
 436 }
 437
 438 static struct range_list *handle_implied_binop(struct range_list *left_rl, int op, struct range_list *right_rl)
 439 {
 440         struct range_list *res_rl;
 441         struct data_range *left_drange, *right_drange;
 442         sval_t res;
 443
 444         if (!left_rl || !right_rl)
 445                 return NULL;
 446         if (has_actual_ranges(left_rl))
 447                 return NULL;
 448         if (has_actual_ranges(right_rl))
 449                 return NULL;
 450
 451         if (ptr_list_size((struct ptr_list *)left_rl) * ptr_list_size((struct ptr_list *)right_rl) > 20)
 452                 return NULL;
 453
 454         res_rl = NULL;
 455
 456         FOR_EACH_PTR(left_rl, left_drange) {
 457                 FOR_EACH_PTR(right_rl, right_drange) {
 458                         if ((op == '%' || op == '/') &&
 459                             right_drange->min.value == 0)
 460                                 return NULL;
 461                         res = sval_binop(left_drange->min, op, right_drange->min);
 462                         add_range(&res_rl, res, res);
 463                 } END_FOR_EACH_PTR(right_drange);
 464         } END_FOR_EACH_PTR(left_drange);
 465
 466         return res_rl;
 467 }
 468
 469 static struct range_list *handle_binop_rl(struct expression *expr, int implied, int *recurse_cnt)
 470 {
 471         struct symbol *type;
 472         struct range_list *left_rl, *right_rl, *rl;
 473         sval_t min, max;
 474
 475         rl = handle_known_binop(expr);
 476         if (rl)
 477                 return rl;
 478         if (implied == RL_EXACT)
 479                 return NULL;
 480
 481         type = get_type(expr);
 482         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 483         left_rl = cast_rl(type, left_rl);
 484         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 485         right_rl = cast_rl(type, right_rl);
 486
 487         rl = handle_implied_binop(left_rl, expr->op, right_rl);
 488         if (rl)
 489                 return rl;
 490
 491         switch (expr->op) {
 492         case '%':
 493                 return handle_mod_rl(expr, implied, recurse_cnt);
 494         case '&':
 495                 return handle_bitwise_AND(expr, implied, recurse_cnt);
 496         case '|':
 497                 return handle_bitwise_OR(expr, implied, recurse_cnt);
 498         case SPECIAL_RIGHTSHIFT:
 499                 return handle_right_shift(expr, implied, recurse_cnt);
 500         case SPECIAL_LEFTSHIFT:
 501                 return handle_left_shift(expr, implied, recurse_cnt);
 502         case '-':
 503                 return handle_subtract_rl(expr, implied, recurse_cnt);
 504         case '/':
 505                 return handle_divide_rl(expr, implied, recurse_cnt);
 506         }
 507
 508         if (!left_rl || !right_rl)
 509                 return NULL;
 510
 511         if (sval_binop_overflows(rl_min(left_rl), expr->op, rl_min(right_rl)))
 512                 return NULL;
 513         min = sval_binop(rl_min(left_rl), expr->op, rl_min(right_rl));
 514
 515         if (sval_binop_overflows(rl_max(left_rl), expr->op, rl_max(right_rl))) {
 516                 switch (implied) {
 517                 case RL_FUZZY:
 518                 case RL_HARD:
 519                         return NULL;
 520                 default:
 521                         max = sval_type_max(get_type(expr));
 522                 }
 523         } else {
 524                 max = sval_binop(rl_max(left_rl), expr->op, rl_max(right_rl));
 525         }
 526
 527         return alloc_rl(min, max);
 528 }
 529
 530 static int do_comparison(struct expression *expr)
 531 {
 532         struct range_list *left_ranges = NULL;
 533         struct range_list *right_ranges = NULL;
 534         int poss_true, poss_false;
 535         struct symbol *type;
 536
 537         type = get_type(expr);
 538         get_absolute_rl(expr->left, &left_ranges);
 539         get_absolute_rl(expr->right, &right_ranges);
 540
 541         left_ranges = cast_rl(type, left_ranges);
 542         right_ranges = cast_rl(type, right_ranges);
 543
 544         poss_true = possibly_true_rl(left_ranges, expr->op, right_ranges);
 545         poss_false = possibly_false_rl(left_ranges, expr->op, right_ranges);
 546
 547         free_rl(&left_ranges);
 548         free_rl(&right_ranges);
 549
 550         if (!poss_true && !poss_false)
 551                 return 0x0;
 552         if (poss_true && !poss_false)
 553                 return 0x1;
 554         if (!poss_true && poss_false)
 555                 return 0x2;
 556         return 0x3;
 557 }
 558
 559 static struct range_list *handle_comparison_rl(struct expression *expr, int implied)
 560 {
 561         sval_t left, right;
 562         int res;
 563
 564         if (get_value(expr->left, &left) && get_value(expr->right, &right)) {
 565                 struct data_range tmp_left, tmp_right;
 566
 567                 tmp_left.min = left;
 568                 tmp_left.max = left;
 569                 tmp_right.min = right;
 570                 tmp_right.max = right;
 571                 if (true_comparison_range(&tmp_left, expr->op, &tmp_right))
 572                         return rl_one();
 573                 return rl_zero();
 574         }
 575
 576         if (implied == RL_EXACT)
 577                 return NULL;
 578
 579         res = do_comparison(expr);
 580         if (res == 1)
 581                 return rl_one();
 582         if (res == 2)
 583                 return rl_zero();
 584
 585         return alloc_rl(zero, one);
 586 }
 587
 588 static struct range_list *handle_logical_rl(struct expression *expr, int implied)
 589 {
 590         sval_t left, right;
 591         int left_known = 0;
 592         int right_known = 0;
 593
 594         if (implied == RL_EXACT) {
 595                 if (get_value(expr->left, &left))
 596                         left_known = 1;
 597                 if (get_value(expr->right, &right))
 598                         right_known = 1;
 599         } else {
 600                 if (get_implied_value(expr->left, &left))
 601                         left_known = 1;
 602                 if (get_implied_value(expr->right, &right))
 603                         right_known = 1;
 604         }
 605
 606         switch (expr->op) {
 607         case SPECIAL_LOGICAL_OR:
 608                 if (left_known && left.value)
 609                         return rl_one();
 610                 if (right_known && right.value)
 611                         return rl_one();
 612                 if (left_known && right_known)
 613                         return rl_zero();
 614                 break;
 615         case SPECIAL_LOGICAL_AND:
 616                 if (left_known && right_known) {
 617                         if (left.value && right.value)
 618                                 return rl_one();
 619                         return rl_zero();
 620                 }
 621                 break;
 622         default:
 623                 return NULL;
 624         }
 625
 626         if (implied == RL_EXACT)
 627                 return NULL;
 628
 629         return alloc_rl(zero, one);
 630 }
 631
 632 static struct range_list *handle_conditional_rl(struct expression *expr, int implied, int *recurse_cnt)
 633 {
 634         struct range_list *true_rl, *false_rl;
 635         struct symbol *type;
 636         int final_pass_orig = final_pass;
 637
 638         if (known_condition_true(expr->conditional))
 639                 return _get_rl(expr->cond_true, implied, recurse_cnt);
 640         if (known_condition_false(expr->conditional))
 641                 return _get_rl(expr->cond_false, implied, recurse_cnt);
 642
 643         if (implied == RL_EXACT)
 644                 return NULL;
 645
 646         if (implied_condition_true(expr->conditional))
 647                 return _get_rl(expr->cond_true, implied, recurse_cnt);
 648         if (implied_condition_false(expr->conditional))
 649                 return _get_rl(expr->cond_false, implied, recurse_cnt);
 650
 651
 652         /* this becomes a problem with deeply nested conditional statements */
 653         if (low_on_memory())
 654                 return NULL;
 655
 656         type = get_type(expr);
 657
 658         __push_fake_cur_stree();
 659         final_pass = 0;
 660         __split_whole_condition(expr->conditional);
 661         true_rl = _get_rl(expr->cond_true, implied, recurse_cnt);
 662         __push_true_states();
 663         __use_false_states();
 664         false_rl = _get_rl(expr->cond_false, implied, recurse_cnt);
 665         __merge_true_states();
 666         __free_fake_cur_stree();
 667         final_pass = final_pass_orig;
 668
 669         if (!true_rl || !false_rl)
 670                 return NULL;
 671         true_rl = cast_rl(type, true_rl);
 672         false_rl = cast_rl(type, false_rl);
 673
 674         return rl_union(true_rl, false_rl);
 675 }
 676
 677 static int get_fuzzy_max_helper(struct expression *expr, sval_t *max)
 678 {
 679         struct smatch_state *state;
 680         sval_t sval;
 681
 682         if (get_hard_max(expr, &sval)) {
 683                 *max = sval;
 684                 return 1;
 685         }
 686
 687         state = get_extra_state(expr);
 688         if (!state || !estate_has_fuzzy_max(state))
 689                 return 0;
 690         *max = sval_cast(get_type(expr), estate_get_fuzzy_max(state));
 691         return 1;
 692 }
 693
 694 static int get_fuzzy_min_helper(struct expression *expr, sval_t *min)
 695 {
 696         struct smatch_state *state;
 697         sval_t sval;
 698
 699         state = get_extra_state(expr);
 700         if (!state || !estate_rl(state))
 701                 return 0;
 702
 703         sval = estate_min(state);
 704         if (sval_is_negative(sval) && sval_is_min(sval))
 705                 return 0;
 706
 707         if (sval_is_max(sval))
 708                 return 0;
 709
 710         *min = sval_cast(get_type(expr), sval);
 711         return 1;
 712 }
 713
 714 int get_const_value(struct expression *expr, sval_t *sval)
 715 {
 716         struct symbol *sym;
 717         sval_t right;
 718
 719         if (expr->type != EXPR_SYMBOL || !expr->symbol)
 720                 return 0;
 721         sym = expr->symbol;
 722         if (!(sym->ctype.modifiers & MOD_CONST))
 723                 return 0;
 724         if (get_value(sym->initializer, &right)) {
 725                 *sval = sval_cast(get_type(expr), right);
 726                 return 1;
 727         }
 728         return 0;
 729 }
 730
 731 struct range_list *var_to_absolute_rl(struct expression *expr)
 732 {
 733         struct smatch_state *state;
 734         struct range_list *rl;
 735
 736         state = get_extra_state(expr);
 737         if (!state) {
 738                 if (get_local_rl(expr, &rl))
 739                         return rl;
 740                 if (get_db_type_rl(expr, &rl))
 741                         return rl;
 742                 return alloc_whole_rl(get_type(expr));
 743         }
 744         /* err on the side of saying things are possible */
 745         if (!estate_rl(state))
 746                 return alloc_whole_rl(get_type(expr));
 747         return clone_rl(estate_rl(state));
 748 }
 749
 750 static struct range_list *handle_variable(struct expression *expr, int implied, int *recurse_cnt)
 751 {
 752         struct smatch_state *state;
 753         struct range_list *rl;
 754         sval_t sval, min, max;
 755
 756         if (get_const_value(expr, &sval))
 757                 return alloc_rl(sval, sval);
 758
 759         if (custom_handle_variable) {
 760                 rl = custom_handle_variable(expr);
 761                 if (!rl)
 762                         return var_to_absolute_rl(expr);
 763                 return rl;
 764         }
 765
 766         switch (implied) {
 767         case RL_EXACT:
 768                 return NULL;
 769         case RL_HARD:
 770         case RL_IMPLIED:
 771         case RL_ABSOLUTE:
 772                 state = get_extra_state(expr);
 773                 if (!state || !state->data) {
 774                         if (implied == RL_HARD)
 775                                 return NULL;
 776                         if (get_local_rl(expr, &rl))
 777                                 return rl;
 778                         if (get_db_type_rl(expr, &rl))
 779                                 return rl;
 780                         return NULL;
 781                 }
 782                 if (implied == RL_HARD && !estate_has_hard_max(state))
 783                         return NULL;
 784                 return clone_rl(estate_rl(state));
 785         case RL_FUZZY:
 786                 if (!get_fuzzy_min_helper(expr, &min))
 787                         min = sval_type_min(get_type(expr));
 788                 if (!get_fuzzy_max_helper(expr, &max))
 789                         return NULL;
 790                 /* fuzzy ranges are often inverted */
 791                 if (sval_cmp(min, max) > 0) {
 792                         sval = min;
 793                         min = max;
 794                         max = sval;
 795                 }
 796                 return alloc_rl(min, max);
 797         }
 798         return NULL;
 799 }
 800
 801 static sval_t handle_sizeof(struct expression *expr)
 802 {
 803         struct symbol *sym;
 804         sval_t ret;
 805
 806         ret = sval_blank(expr);
 807         sym = expr->cast_type;
 808         if (!sym) {
 809                 sym = evaluate_expression(expr->cast_expression);
 810                 /*
 811                  * Expressions of restricted types will possibly get
 812                  * promoted - check that here
 813                  */
 814                 if (is_restricted_type(sym)) {
 815                         if (type_bits(sym) < bits_in_int)
 816                                 sym = &int_ctype;
 817                 } else if (is_fouled_type(sym)) {
 818                         sym = &int_ctype;
 819                 }
 820         }
 821         examine_symbol_type(sym);
 822
 823         ret.type = size_t_ctype;
 824         if (type_bits(sym) <= 0) /* sizeof(void) */ {
 825                 if (get_real_base_type(sym) == &void_ctype)
 826                         ret.value = 1;
 827                 else
 828                         ret.value = 0;
 829         } else
 830                 ret.value = type_bytes(sym);
 831
 832         return ret;
 833 }
 834
 835 static struct range_list *handle_call_rl(struct expression *expr, int implied, int *recurse_cnt)
 836 {
 837         struct range_list *rl;
 838
 839         if (sym_name_is("__builtin_expect", expr->fn)) {
 840                 struct expression *arg;
 841
 842                 arg = get_argument_from_call_expr(expr->args, 0);
 843                 return _get_rl(arg, implied, recurse_cnt);
 844         }
 845
 846         if (implied == RL_EXACT || implied == RL_HARD || implied == RL_FUZZY)
 847                 return NULL;
 848
 849         if (get_implied_return(expr, &rl))
 850                 return rl;
 851         return db_return_vals(expr);
 852 }
 853
 854 static struct range_list *handle_cast(struct expression *expr, int implied, int *recurse_cnt)
 855 {
 856         struct range_list *rl;
 857         struct symbol *type;
 858
 859         type = get_type(expr);
 860         rl = _get_rl(expr->cast_expression, implied, recurse_cnt);
 861         if (rl)
 862                 return cast_rl(type, rl);
 863         if (implied == RL_ABSOLUTE)
 864                 return alloc_whole_rl(type);
 865         if (implied == RL_IMPLIED && type &&
 866             type_bits(type) > 0 && type_bits(type) < 32)
 867                 return alloc_whole_rl(type);
 868         return NULL;
 869 }
 870
 871 static struct range_list *_get_rl(struct expression *expr, int implied, int *recurse_cnt)
 872 {
 873         struct range_list *rl;
 874         struct symbol *type;
 875         sval_t sval;
 876
 877         type = get_type(expr);
 878         expr = strip_parens(expr);
 879         if (!expr)
 880                 return NULL;
 881
 882         if (++(*recurse_cnt) >= 200)
 883                 return NULL;
 884
 885         switch(expr->type) {
 886         case EXPR_CAST:
 887         case EXPR_FORCE_CAST:
 888         case EXPR_IMPLIED_CAST:
 889                 rl = handle_cast(expr, implied, recurse_cnt);
 890                 goto out_cast;
 891         }
 892
 893         expr = strip_expr(expr);
 894         if (!expr)
 895                 return NULL;
 896
 897         switch (expr->type) {
 898         case EXPR_VALUE:
 899                 sval = sval_from_val(expr, expr->value);
 900                 rl = alloc_rl(sval, sval);
 901                 break;
 902         case EXPR_PREOP:
 903                 rl = handle_preop_rl(expr, implied, recurse_cnt);
 904                 break;
 905         case EXPR_POSTOP:
 906                 rl = _get_rl(expr->unop, implied, recurse_cnt);
 907                 break;
 908         case EXPR_BINOP:
 909                 rl = handle_binop_rl(expr, implied, recurse_cnt);
 910                 break;
 911         case EXPR_COMPARE:
 912                 rl = handle_comparison_rl(expr, implied);
 913                 break;
 914         case EXPR_LOGICAL:
 915                 rl = handle_logical_rl(expr, implied);
 916                 break;
 917         case EXPR_PTRSIZEOF:
 918         case EXPR_SIZEOF:
 919                 sval = handle_sizeof(expr);
 920                 rl = alloc_rl(sval, sval);
 921                 break;
 922         case EXPR_SELECT:
 923         case EXPR_CONDITIONAL:
 924                 rl = handle_conditional_rl(expr, implied, recurse_cnt);
 925                 break;
 926         case EXPR_CALL:
 927                 rl = handle_call_rl(expr, implied, recurse_cnt);
 928                 break;
 929         default:
 930                 rl = handle_variable(expr, implied, recurse_cnt);
 931         }
 932
 933 out_cast:
 934         if (rl)
 935                 return rl;
 936         if (type && implied == RL_ABSOLUTE)
 937                 return alloc_whole_rl(type);
 938         return NULL;
 939 }
 940
 941 /* returns 1 if it can get a value literal or else returns 0 */
 942 int get_value(struct expression *expr, sval_t *sval)
 943 {
 944         struct range_list *rl;
 945         int recurse_cnt = 0;
 946
 947         rl = _get_rl(expr, RL_EXACT, &recurse_cnt);
 948         if (!rl_to_sval(rl, sval))
 949                 return 0;
 950         return 1;
 951 }
 952
 953 int get_implied_value(struct expression *expr, sval_t *sval)
 954 {
 955         struct range_list *rl;
 956         int recurse_cnt = 0;
 957
 958         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
 959         if (!rl_to_sval(rl, sval))
 960                 return 0;
 961         return 1;
 962 }
 963
 964 int get_implied_min(struct expression *expr, sval_t *sval)
 965 {
 966         struct range_list *rl;
 967         int recurse_cnt = 0;
 968
 969         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
 970         if (!rl)
 971                 return 0;
 972         *sval = rl_min(rl);
 973         return 1;
 974 }
 975
 976 int get_implied_max(struct expression *expr, sval_t *sval)
 977 {
 978         struct range_list *rl;
 979         int recurse_cnt = 0;
 980
 981         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
 982         if (!rl)
 983                 return 0;
 984         *sval = rl_max(rl);
 985         return 1;
 986 }
 987
 988 int get_implied_rl(struct expression *expr, struct range_list **rl)
 989 {
 990         int recurse_cnt = 0;
 991
 992         *rl = _get_rl(expr, RL_IMPLIED, &recurse_cnt);
 993         if (*rl)
 994                 return 1;
 995         return 0;
 996 }
 997
 998 int get_absolute_rl(struct expression *expr, struct range_list **rl)
 999 {
1000         int recurse_cnt = 0;
1001
1002         *rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1003         if (!*rl)
1004                 *rl = alloc_whole_rl(get_type(expr));
1005         return 1;
1006 }
1007
1008 int custom_get_absolute_rl(struct expression *expr,
1009                            struct range_list *(*fn)(struct expression *expr),
1010                            struct range_list **rl)
1011 {
1012         int recurse_cnt = 0;
1013
1014         *rl = NULL;
1015         custom_handle_variable = fn;
1016         *rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1017         custom_handle_variable = NULL;
1018         return 1;
1019 }
1020
1021 int get_implied_rl_var_sym(const char *var, struct symbol *sym, struct range_list **rl)
1022 {
1023         struct smatch_state *state;
1024
1025         state = get_state(SMATCH_EXTRA, var, sym);
1026         *rl = estate_rl(state);
1027         if (*rl)
1028                 return 1;
1029         return 0;
1030 }
1031
1032 int get_hard_max(struct expression *expr, sval_t *sval)
1033 {
1034         struct range_list *rl;
1035         int recurse_cnt = 0;
1036
1037         rl =  _get_rl(expr, RL_HARD, &recurse_cnt);
1038         if (!rl)
1039                 return 0;
1040         *sval = rl_max(rl);
1041         return 1;
1042 }
1043
1044 int get_fuzzy_min(struct expression *expr, sval_t *sval)
1045 {
1046         struct range_list *rl;
1047         sval_t tmp;
1048         int recurse_cnt = 0;
1049
1050         rl =  _get_rl(expr, RL_FUZZY, &recurse_cnt);
1051         if (!rl)
1052                 return 0;
1053         tmp = rl_min(rl);
1054         if (sval_is_negative(tmp) && sval_is_min(tmp))
1055                 return 0;
1056         *sval = tmp;
1057         return 1;
1058 }
1059
1060 int get_fuzzy_max(struct expression *expr, sval_t *sval)
1061 {
1062         struct range_list *rl;
1063         sval_t max;
1064         int recurse_cnt = 0;
1065
1066         rl =  _get_rl(expr, RL_FUZZY, &recurse_cnt);
1067         if (!rl)
1068                 return 0;
1069         max = rl_max(rl);
1070         if (max.uvalue > INT_MAX - 10000)
1071                 return 0;
1072         *sval = max;
1073         return 1;
1074 }
1075
1076 int get_absolute_min(struct expression *expr, sval_t *sval)
1077 {
1078         struct range_list *rl;
1079         struct symbol *type;
1080         int recurse_cnt = 0;
1081
1082         type = get_type(expr);
1083         if (!type)
1084                 type = &llong_ctype;  // FIXME: this is wrong but places assume get type can't fail.
1085         rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1086         if (rl)
1087                 *sval = rl_min(rl);
1088         else
1089                 *sval = sval_type_min(type);
1090
1091         if (sval_cmp(*sval, sval_type_min(type)) < 0)
1092                 *sval = sval_type_min(type);
1093         return 1;
1094 }
1095
1096 int get_absolute_max(struct expression *expr, sval_t *sval)
1097 {
1098         struct range_list *rl;
1099         struct symbol *type;
1100         int recurse_cnt = 0;
1101
1102         type = get_type(expr);
1103         if (!type)
1104                 type = &llong_ctype;
1105         rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1106         if (rl)
1107                 *sval = rl_max(rl);
1108         else
1109                 *sval = sval_type_max(type);
1110
1111         if (sval_cmp(sval_type_max(type), *sval) < 0)
1112                 *sval = sval_type_max(type);
1113         return 1;
1114 }
1115
1116 int known_condition_true(struct expression *expr)
1117 {
1118         sval_t tmp;
1119
1120         if (!expr)
1121                 return 0;
1122
1123         if (get_value(expr, &tmp) && tmp.value)
1124                 return 1;
1125
1126         return 0;
1127 }
1128
1129 int known_condition_false(struct expression *expr)
1130 {
1131         if (!expr)
1132                 return 0;
1133
1134         if (is_zero(expr))
1135                 return 1;
1136
1137         if (expr->type == EXPR_CALL) {
1138                 if (sym_name_is("__builtin_constant_p", expr->fn))
1139                         return 1;
1140         }
1141         return 0;
1142 }
1143
1144 int implied_condition_true(struct expression *expr)
1145 {
1146         sval_t tmp;
1147
1148         if (!expr)
1149                 return 0;
1150
1151         if (known_condition_true(expr))
1152                 return 1;
1153         if (get_implied_value(expr, &tmp) && tmp.value)
1154                 return 1;
1155
1156         if (expr->type == EXPR_POSTOP)
1157                 return implied_condition_true(expr->unop);
1158
1159         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_DECREMENT)
1160                 return implied_not_equal(expr->unop, 1);
1161         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_INCREMENT)
1162                 return implied_not_equal(expr->unop, -1);
1163
1164         expr = strip_expr(expr);
1165         switch (expr->type) {
1166         case EXPR_COMPARE:
1167                 if (do_comparison(expr) == 1)
1168                         return 1;
1169                 break;
1170         case EXPR_PREOP:
1171                 if (expr->op == '!') {
1172                         if (implied_condition_false(expr->unop))
1173                                 return 1;
1174                         break;
1175                 }
1176                 break;
1177         default:
1178                 if (implied_not_equal(expr, 0) == 1)
1179                         return 1;
1180                 break;
1181         }
1182         return 0;
1183 }
1184
1185 int implied_condition_false(struct expression *expr)
1186 {
1187         struct expression *tmp;
1188         sval_t sval;
1189
1190         if (!expr)
1191                 return 0;
1192
1193         if (known_condition_false(expr))
1194                 return 1;
1195
1196         switch (expr->type) {
1197         case EXPR_COMPARE:
1198                 if (do_comparison(expr) == 2)
1199                         return 1;
1200         case EXPR_PREOP:
1201                 if (expr->op == '!') {
1202                         if (implied_condition_true(expr->unop))
1203                                 return 1;
1204                         break;
1205                 }
1206                 tmp = strip_expr(expr);
1207                 if (tmp != expr)
1208                         return implied_condition_false(tmp);
1209                 break;
1210         default:
1211                 if (get_implied_value(expr, &sval) && sval.value == 0)
1212                         return 1;
1213                 break;
1214         }
1215         return 0;
1216 }
1217
1218 int can_integer_overflow(struct symbol *type, struct expression *expr)
1219 {
1220         int op;
1221         sval_t lmax, rmax, res;
1222
1223         if (!type)
1224                 type = &int_ctype;
1225
1226         expr = strip_expr(expr);
1227
1228         if (expr->type == EXPR_ASSIGNMENT) {
1229                 switch(expr->op) {
1230                 case SPECIAL_MUL_ASSIGN:
1231                         op = '*';
1232                         break;
1233                 case SPECIAL_ADD_ASSIGN:
1234                         op = '+';
1235                         break;
1236                 case SPECIAL_SHL_ASSIGN:
1237                         op = SPECIAL_LEFTSHIFT;
1238                         break;
1239                 default:
1240                         return 0;
1241                 }
1242         } else if (expr->type == EXPR_BINOP) {
1243                 if (expr->op != '*' && expr->op != '+' && expr->op != SPECIAL_LEFTSHIFT)
1244                         return 0;
1245                 op = expr->op;
1246         } else {
1247                 return 0;
1248         }
1249
1250         get_absolute_max(expr->left, &lmax);
1251         get_absolute_max(expr->right, &rmax);
1252
1253         if (sval_binop_overflows(lmax, op, rmax))
1254                 return 1;
1255
1256         res = sval_binop(lmax, op, rmax);
1257         if (sval_cmp(res, sval_type_max(type)) > 0)
1258                 return 1;
1259         return 0;
1260 }